Apparatus for producing an intermediate in the synthesis of acesulfame potassium

ABSTRACT

The invention discloses a kind of sulfonation cyclization technique for synthesizing acesulfame potassium for continuous production without stirring and special equipment for this technique. An injection pump is adopted to directly inject the sulfonation raw material and sulfonating agent into autoclave for sulfonation cyclization reaction under high velocity. Moreover, the reciprocating pump is adopted to deliver part of materials in autoclave to condenser designed outside the autoclave for cooling, followed by delivering the cooled materials to another input end of injection pump which together with sulfonation raw material and sulfonating agent is injected into autoclave through high-velocity injection by injection pump. The apparatus is composed of autoclave, injection pump, reciprocating pump and condenser.

CROSS-RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/856,969, filed Sept. 18, 2007, which claims priority from ChinesePatent Application No. 2006-10096179.0; filed Sept. 24, 2006, thedisclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a process for production of anintermediate for production of salts of6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2,-dioxide.

BACKGROUND OF THE INVENTION

Acesulfame potassium is one kind of sweetener widely used in foodstuffand beverage industry, which is characterized by good water solubility,high saccharinity, stable physicochemical property, strong synergizedaction and non-metabolism.

There are many ways to synthesize acesulfame potassium. A synthesis ofacesulfame potassium is proposed in U.S. Pat. No. 4,695,629, wherein thereaction between raw material sulfamic acid and diketene is carried outby catalysis of triethylamine, followed by conducting sulfonationcyclization with sulfur trioxide and hydrolyzing to obtain acesulfamepotassium. Other patents disclosing methods of synthesizing include U.S.Pat. Nos. 5,011,982 and 5,103,046. No special reaction equipmentrelating to sulfonation cyclization of sulfur trioxide and hydrolizationhas been found in other patents relating to synthesis of acesulfamepotassium with sulfur trioxide as the sulfonating agent such as withrespect to sulfonation cyclization reaction mentioned in these patents,generally, sulfonation raw material and sulfonating agent are added intoautoclave for sulfonation cyclization reaction and the autoclaveincludes a stirring device to promote reaction. However, a cooling brinemust be added into the jacket of autoclave during reaction to cool theheat discharged during reaction and control reaction temperature.

Research indicates that sulfur trioxide is a strong corrosive agent,oxidant, smoke substance and the adoption of common reaction equipmentto carry out sulfonation cyclization reaction can easily result inleakage of sulfur trioxide, especially leakage easily occurs on themechanical seal due to wear and tear by stirring. The leakage of sulfurtrioxide may exert great negative impact on production and theenvironment since sulfur trioxide is a dangerous chemical product. Inaddition, only intermittent production can be conducted in terms of thistype of reaction and the efficiency is low, while continuous productioncannot be realized.

SUMMARY OF THE INVENTION

The present invention provides a process for continuous production of anintermediate used in the production of salts of6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2,-dioxide. The processcomprises the first step of injecting a sulfonation raw material and asulfonating reagent into a reactor, wherein said sulfonation rawmaterial and sulfonating reagent are dissolved in an organic solvent toprovide a reaction mixture of the sulfonation raw material andsulfonating reagent. Then a portion of the reaction mixture is removedfrom the reactor and cooled separate from the reaction mixture in thereactor. The cooled portion of the reaction mixture is combined backwith the reaction mixture in that the reactor cyclization is allowed tooccur to provide the desired intermediate in the synthesis of acesulfamepotassium.

The present invention also provides an apparatus for the continuousproduction of the intermediate.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

FIG. 1 illustrates an apparatus for production of the intermediate forsulfonation cyclization technique mentioned in the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Further descriptions on the invention disclosed herein will be made inthe following on the basis of attached drawing and specific procedures.

Technical matters to be dealt with in the invention disclosed hereinrelates to a kind of sulfonation cyclization technique for synthesizingacesulfame potassium for continuous production without stirring andspecial equipment for the technique (e.g., liquid SO₃ or methylenechloride).

For the purpose of dealing with the above technical matters, the majortechnical principle elaborated in the invention is as follows:sulfonation raw material and sulfonating agent such as those detailed inU.S. Pat. Nos. 4,695,629 and 4,876,341, the disclosures of which arehereby incorporated by reference in their entireties, are injected intoa reactor (e.g., an autoclave) through high-velocity injection by aninjection pump to form a vortex to provide a reaction mixture. In oneembodiment, the mol ratio of sulfonating agent to raw material is about3 to 7 mol to 1 mol raw material, in another embodiment is 4 to 7 mol to1 mol raw material, and in yet another embodiment is about 4 mol to 1mol raw material. The raw material and sulfonating agent can bedissolved in an organic solvent such as, for example, a halogenatedalkyl or alkene or an alkylene solvent (e.g., CHCl₃ or tetrachlorideethylene). A portion of the reaction mixture is removed and delivered,via a circulating pump, to a condenser for cooling. The cooled reactionmixture is returned to the reactor mixture and the remaining reactionmixture. In this manner, the need for a stirring device is eliminatedand problems concerning leakage and intermittent production can besolved.

After the sulfonation cyclization reaction is complete, the resultantmaterial (i.e., the desired intermediate) is discharged at the bottom ofautoclave, and is then used to synthesize salts of6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2,-dioxide.

The temperature of aforesaid material which has been cooled in condensercan be preferably controlled at −50° C. to about −15° C., and in oneembodiment is controlled at about −45° C. to about −20° C.

The apparatus used in sulfonation cyclization technique includesautoclave, feed opening and feed back hole designed on the side wall ofautoclave with the feed opening locating below feed back hole, dischargehole at the bottom of autoclave, and feed opening connected to theoutlet of injection pump, and feed back hole connected to the inlet ofreciprocating pump, and the outlet of reciprocating pump connected tothe inlet of condenser, and the outlet of condenser connected to oneinput end of injection pump and two input ends of injection pumpseparately connected to sulfonation raw material and sulfonating agent.

As indicated in FIG. 1, the apparatus for the aforesaid sulfonationcyclization technique includes autoclave 1, feed opening 10 and feedback hole 8 designed on the side wall of autoclave 1 with the feedopening 10 locating below feed back hole 8, discharge hole 11 at thebottom of autoclave 1, and feed opening 10 connected to the outlet 7 ofinjection pump 6, and feed back hole 8 connected to the inlet ofreciprocating pump 9, and the outlet of reciprocating pump 9 connectedto the inlet of condenser 5, and the outlet of condenser 5 connected toone input end 4 of injection pump 6 and two input ends of injection pump6 separately connected to sulfonation raw material 2 and sulfonatingagent 3.

Sulfonation cyclization technique mentioned in the invention disclosedherein with adoption of the aforesaid apparatus is detailed as follows:the sulfonation raw material 2 and sulfonating agent 3 are separatelydelivered into two input ends of injection pump 6, which are directlyinjected into autoclave 1 for sulfonation cyclization reaction byinjection pump 6; meanwhile, reciprocating pump 9 is adopted to delivera portion of the reaction mixture in autoclave 1 to condenser 5 forcooling, with temperature of material which has been cooled in condenser5 being controlled at −50° C. to about −15° C., followed by deliveringthe cooled reaction mixture to another input end 4 of injection pump 6which together with sulfonation raw material 2 and sulfonating agent 3is injected into autoclave 1 through high-velocity injection byinjection pump 6. After the sulfonation cyclization reaction, theresultant materials are discharged through discharge hole 11 at thebottom of autoclave 1.

Based on the above, negative pressure generated during high-velocityinjection by injection pump 6 is more conducive to injecting sulfonationraw material 2, sulfonating agent 3 and materials cooled in condenser 5into autoclave 1 to form a vortex on the inside wall of autoclave 1,thus allowing the complete sulfonation cyclization reaction to occurwithout stirring. Moreover, removing a portion of the reaction mixturefor cooling outside the autoclave 1 can better control the temperatureof reactants; therefore, sulfonation cyclization technique and apparatusfor the technique mentioned in the invention disclosed herein can bringabout continuous production and greatly improve productivity.

1. An apparatus for carrying out sulfonation cyclization to reduce theleakage of a sulfonating reagent during continuous production of thesalts of 6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2,-dioxidecomprising: (a) a down stream reactor to carry out a sulfonationcyclization reaction, (b) an injection pump to introduce the mixture ofthe sulfonation raw material and the sulfonating reagent into thedownstream reactor, (c) a reciprocating pump to remove a portion of thereaction mixture, and (d) means for cooling the portion of the reactionmixture removed from the reactor.
 2. The apparatus of claim 1, whereinthe cooled portion of the reaction mixture is delivered to the injectionpump and the injection pump injects a mixture of the sulfonation rawmaterial, the sufonating reagent and the cooled portion into thereactor.
 3. The apparatus of claim 1, wherein said reactor comprising afeed inlet and a feed outlet on the sidewall of the reactor, and adischarge outlet at the bottom of the reactor.
 4. The apparatus of claim3, wherein the feed inlet of the reactor is connected to the outlet ofthe injection pump, the feed outlet of the reactor is connected to theinlet of the reciprocating pump, the outlet of the reciprocating pump isconnected to the inlet of the means for cooling and the outlet of themeans for cooling is connected to at least one inlet of the injectionpump.
 5. The apparatus of claim 1, wherein the means for cooling and theinjection pump are positioned above the reactor and the reciprocatingpump.
 6. The apparatus of claim 1, wherein said reactor is an autoclave.7. The apparatus of claim 1, wherein said means for cooling is acondenser.